My battle pet, Lantesh, is "Bloated" and "Very Happy", but at the Battledome I keep getting told, "Oh no! None of your pets are eligible for battle. You might want to make sure that they're well fed and happy!" Why? I want to do the third room!

Make sure your pet is also healed.

I tried that and got the same message. Here are Lantesh's stats, if it will help at all. Hunger: Bloated Happiness: Very Happy Level: 327 Health: 814/814 Strength: 790 Defense: 790 Speed: 781 Intelligence: 12 Pet Rank: 1,054

Was the pet recently transferred via "Send Pet to Friend"?

No, I've had him ever since I created him. He's never been pounded or transferred.

Try a hard refresh -ctrl + F5- on pet page and the battle page. Not sure if it'll help, but its worth a shot.

Have you checked your Battle Statistics page to see if the pet is already in a battle that hasn't been completed?

Aha! That was it. Problem solved. Thanks ever so much! :D